1. Field
The disclosed embodiments generally relate to techniques for delivering DC power at different potentials. More specifically, the disclosed embodiments relate to a high-efficiency, switched-capacitor power-conversion technique, which uses a resonant clocking circuit to produce gate drive signals for switching transistors.
2. Related Art
Battery performance is critical to the effective operation of portable computing devices, such as laptop computers. To provide higher supply voltages, battery cells inside portable computing devices are typically stacked in series inside a battery pack. This arrangement provides power efficiently because conduction losses are lower in such a series arrangement. Unfortunately, providing power in this way is inefficient when the power is subsequently down-converted to provide lower voltages for certain system components. For example, the power is usually down-converted using buck converters or other down-conversion techniques that achieve only a 90% efficiency or worse. (Note that power=I·V, whereas conduction loss is proportional to I2R.)
A battery management unit (BMU) typically controls the charging and discharging processes for a battery pack. However, if the battery cells that comprise the battery pack are not matched in capacity, the battery pack can suffer from an imbalance condition. An imbalanced battery pack has reduced capacity because the cell with the highest state-of-charge will cause the charging process to terminate, which means that cells with a lower state-of-charge never get fully charged. Additionally, when the battery pack is discharged, the cell with the least charge may cause the discharging process to stop, even though charge may remain in other cells.
As an alternative to arranging battery cells in series to achieve higher voltages, voltage converters can be used to increase output voltages. However, existing voltage converter designs suffer from inefficiencies which are a significant power loss.